The present invention relates to an assembly for the compressed air supply of a wheel of a vehicle, in particular of a motor vehicle. By means of the assembly, the tire pressure in the wheel of the vehicle can be varied while traveling.
The practice of varying the tire pressure in a vehicle can have a positive effect both on the traveling comfort and on the energy consumption. By way of example, an appropriately low tire pressure leads to a soft suspension in the tire and therefore to a more comfortable journey. An appropriately high tire pressure reduces the rolling resistance. This in turn reduces the energy consumption of the vehicle and thereby improves the CO2 footprint. A constant problem with the construction of the compressed air supply is the guidance of compressed air from the compressed-air source in the vehicle to the rotating wheel. The document US2008/0006357A1 discloses an exemplary solution in this regard. In said document, the air is guided through appropriate bores and lines in the wheel suspension. However, bores of this nature should be dispensed with as far as possible, since each bore always has the disadvantage that it is complex to manufacture and weakens the corresponding component.
It is an object of the present invention to provide an assembly for the supply of compressed air to a wheel of a vehicle which allows for reliable and sustained operation both of the vehicle and also of the compressed air supply given inexpensive production and assembly. Furthermore, it is an object of the present invention to provide a corresponding method for tire inflation pressure regulation of the wheel.
This and other objects are achieved by an assembly and method according to embodiments of the invention.
According to the invention, an assembly is provided for the compressed air supply of a wheel of a vehicle. This assembly comprises a wheel with a tire and also an output (drive) shaft. The output shaft serves for transmitting torque to the wheel. Accordingly, the output shaft leads from the engine of the vehicle via any possible gear mechanisms to the wheel suspension.
The wheel is mounted on a wheel bearing of the assembly in a rotationally fixed manner. A toothing system is provided between the output shaft and the wheel bearing. The toothing system serves for transmitting torque from the output shaft to the wheel bearing. The wheel bearing is braced to the output shaft by means of a bolt. Said bolt extends coaxially to the output shaft in an inner hollow space of the wheel bearing. What is termed a wheel bearing annular space is defined in said hollow space radially outside the bolt. According to the invention, at least one compressed-air passage is provided from the wheel bearing annular space in the direction of the wheel. Furthermore, the assembly includes a compressed-air guide. This leads from a vehicle-side compressed-air source into the wheel bearing annular space and from the wheel bearing annular space through the at least one compressed-air passage to the wheel. In the wheel, the compressed air can be guided radially outward, for example through the spokes, to the rim and into the tire. According to the invention, provision is therefore made to utilize the wheel bearing annular space for guiding the compressed air. Accordingly, the at least one compressed-air passage is provided for conducting the compressed air introduced into the wheel bearing annular space further in the direction of the wheel.
In an advantageous embodiment, it is provided that a bolt head of the bolt bears against a contact surface on the wheel bearing. The at least one compressed-air passage is formed in the region of the contact surface, in the wheel bearing and/or in the bolt. In order to conduct the compressed air from the wheel bearing annular space further in the direction of the wheel, the compressed air has to be guided through the contact surface or close to the contact surface (i.e. in the wheel bearing) or through the bolt.
In the text which follows, different embodiments of the at least one compressed-air passage will be described. In this respect, it will always be appreciated that a plurality of the compressed-air passages can also be formed in the one assembly. In this context, it is also possible for the plurality of compressed-air passages to have different configurations. Thus, by way of example, one compressed-air passage may be present as a groove and another compressed-air passage may be present as a channel.
It is preferably provided that the compressed-air passage is formed by a groove in the wheel bearing on the contact surface and/or by a groove in the bolt head on the contact surface. A groove of this nature on the contact surface ensures that the bolt head does not completely seal off the wheel bearing annular space on the contact surface, but rather the compressed air can be guided through the groove further in the direction of the wheel.
Furthermore, it is preferably provided to form the compressed-air passage by a channel in the wheel bearing and/or by a channel in the bolt head. The channel in this respect is preferably formed as a bore. As an alternative thereto, it is also possible, for example during the casting of the wheel bearing, to insert a corresponding small tube and to encapsulate it by injection molding. The channels are formed so as to be as short as possible and are led merely around the contact surface, such that weakening of the corresponding components is avoided to the greatest possible extent. In this respect, it is possible to design a channel which passes merely through the bolt head. As an alternative or in addition thereto, a first channel can extend along the center axis of the bolt. A radially directed lateral channel encounters said first channel. The radially directed channel preferably extends through the entire bolt and as a result is easy to manufacture.
Furthermore, it is preferably provided to arrange a flat washer on the contact surface. At least one groove or a bore or a corresponding cutout is formed in said flat washer. The compressed air can thereby be conducted through the groove, bore or cutout in the flat washer from the wheel bearing annular space further in the direction of the wheel.
Instead of the flat washer, it is also possible for a spring ring to be arranged on the contact surface. The corresponding undulation of the spring ring in this respect allows for the formation of a compressed-air passage. It goes without saying here that the bolt is not tightened to such an extent that the spring ring bears fully over the entire surface thereof and forms a seal.
The flat washer or the spring ring can also be formed as a non-closed ring, e.g. in a C shape, in which case the open portion forms the cutout for the compressed air.
Furthermore, it is preferably provided to form the compressed-air passage by using an air-permeable, for example porous, material. This air-permeable material is used as part of the wheel bearing and/or as at least part of the bolt or as at least part of the flat washer. Sintered metal, metal foam or porous PTFE foam (polytetrafluoroethylene) is used with preference for the air-permeable material. It is also possible for the material known by the trade name Metapor to be used here as the air-permeable material.
As has already been described in the introduction, the output shaft is connected to the wheel bearing by way of a toothing system. It has been acknowledged that the compressed air can be guided into the wheel bearing annular space through this toothing system, even if the toothing system is embodied as a splined shaft connection. Such a toothing system, even in a design without play, always has clearances. Here, the splined shaft connection is also regarded in general terms as a toothing system, since the splined shaft connection likewise has clearances at the splines (=teeth).
The clearances are located between the heads of the teeth and the opposing valleys between the teeth. Furthermore, even in the case of the design without play, the involute form of the teeth means that there are clearances between the flanks bearing against one another. Therefore, the compressed-air guide described advantageously leads from the vehicle-side compressed-air source through the toothing system into the wheel bearing annular space. Without modifying existing components, the guidance of the compressed air can therefore be routed from the non-rotating portions of the vehicle into the rotating portions. The wheel bearing annular space adjoins the toothing system on the wheel side. Therefore, the described embodiment of the compressed-air passage from the wheel bearing annular space in the direction of the wheel can advantageously be employed particularly when the compressed air is conducted through the toothing system.
Therefore, the compressed-air guide preferably leads from the vehicle-side compressed-air source to a first annular space. The first annular space directly adjoins the toothing system, and therefore the compressed air can be conducted via the first annular space through the clearances between the teeth of the toothing system. The wheel bearing annular space (also: second annular space) is located on the other side of the toothing system. The compressed air is guided from the wheel bearing annular space to the wheel and via the wheel into the tire. The two annular spaces, upstream and downstream of the toothing system in the direction of flow, ensure that the compressed air is conducted via all of the clearances of the toothing system. The sum total of all clearances of the toothing system forms a sufficiently large cross section for the compressed-air guide.
Furthermore, provision is preferably made of a wheel carrier which can be fastened on the vehicle, in particular by way of chassis links. By way of example, the wheel carrier can be in the form of a pivot bearing. The wheel bearing is mounted rotatably with respect to the wheel carrier. By way of example, a rolling bearing is located between the wheel bearing and the wheel carrier.
A compressed-air line is advantageously provided in or on the wheel carrier. The compressed-air line leads to the first annular space. The compressed-air line can be formed here at least in certain places in the interior of the wheel carrier. The compressed-air line is supplied by the compressed-air source in the vehicle. It is also provided in particular here that a compressed-air source is utilized for a plurality of wheels of the vehicle.
The first annular space is advantageously formed by at least one non-rotating portion of the assembly and at least one rotating portion of the assembly. The non-rotating portion of the assembly is advantageously the wheel carrier. The rotating portion of the assembly is formed in this region in particular by the output shaft and/or the wheel bearing. Furthermore, the inner ring of the rolling bearing, which is fixedly connected to the wheel bearing, can likewise delimit the first annular space. The first annular space advantageously directly adjoins the described toothing system, such that the compressed air is distributed via the first annular space directly over all of the clearances of the toothing system. A sealing assembly is preferably located between the non-rotating portion and the rotating portion. The sealing assembly seals off the first annular space with respect to the surroundings.
The sealing assembly advantageously includes at least one sealing lip. The sealing lip is designed in such a manner that it does not seal off the first annular space in the case of a correspondingly low pressure in the first annular space. Since it does not provide a seal in this state, the sealing lip also does not abrade and therefore is not subjected to wear. The sealing lip is moved by the pressure and provides a seal in the process only in the case of a correspondingly high pressure in the first annular space.
Furthermore, provision is preferably made of a control valve, which is arranged downstream of the compressed-air passage, preferably in the hub region of the wheel or in the wheel bearing. After the compressed-air passage, the compressed air therefore flows advantageously into the control valve. After the control valve, the compressed air is guided through the spokes and the rim into the tire. The control valve is advantageously in the form of a pneumatic control valve, with the compressed air being used not only for inflating the tire but also for actuating the control valve.
The invention furthermore encompasses a method for tire inflation pressure regulation of the vehicle, in particular a motor vehicle, comprising the following steps: (i) providing a compressed-air guide from the vehicle into the tire, wherein the tire can be inflated with air pressure from the compressed-air guide. The compressed-air guide can be formed by separate channels and lines. Furthermore, it is also possible to utilize already existing hollow spaces for the compressed-air guide. It is decisive that the compressed-air guide leads from the vehicle-side compressed-air source into the tire. The text which follows refers to “non-rotating portions” of the vehicle and to “rotating portions” of the vehicle. The rotating portions of the vehicle are in particular the wheel bearing, the wheel mounted on the wheel bearing and the tire mounted on the wheel. The wheel in turn usually has a hub region, a plurality of spokes and the rim.
The method furthermore comprises (ii) measuring an actual pressure in the tire using a sensor. The sensor is located in this respect in the rotating portion of the vehicle, i.e. in particular in the wheel bearing, in the wheel or in the tire. (iii) The measured actual pressure is transmitted wirelessly to a control unit. The control unit is located in the non-rotating portion of the vehicle, for example within the vehicle body. A control valve is located in the compressed-air guide, between the compressed-air source and the tire. (iv) The control valve is actuated depending on the transmitted actual pressure. In this case, the control valve can be actuated into at least two switch positions. A first switch position serves for inflating the tire with compressed air from the compressed-air guide. The second switch position serves for letting the compressed air out of the tire into the surroundings.
According to the invention, the wireless transmission of the measured actual pressure means that there is no need for a tethered connection between the rotating portions and the non-rotating portions of the vehicle. Furthermore, the control unit can independently adapt the actual pressure in the tire to a desired target pressure. This is effected by appropriately actuating the control valve depending on the actual pressure. The target pressure can be determined on the one hand by driver stipulation, and on the other hand can be calculated on the basis of vehicle data. Thus, it may be concluded, for example, that an energy-saving mode of driving is appropriate. The target pressure is accordingly increased. If a more comfortable journey is required, the target pressure can be lowered in order to thereby lower the tire rigidity.
It is advantageously provided that the control valve can be actuated pneumatically. In this respect, the control unit varies the pressure in the compressed-air guide depending on the transmitted actual pressure. A first pressure in the compressed-air guide in this respect brings about the first switch position. A second pressure brings about the second switch position. At least two switch positions are therefore provided.
Furthermore, it is advantageously provided that the control valve is located in the rotating portion of the vehicle. In particular, the control valve is arranged, preferably centrically, in the hub region of the wheel or in the wheel bearing. Particularly when the control valve is arranged in the rotating portion of the vehicle, it is advantageous to pneumatically actuate the control valve. As a consequence, there is no need for data-carrying or power-carrying lines, for instance for a solenoid valve, in the rotating portion. The compressed-air guide which is present in any case can also be utilized for signal transmission and for actuating the control valve.
In particular, it is provided that the second pressure for switching into the second switch position is higher than the first pressure for switching into the first switch position. The second switch position is used for letting the air pressure out of the tire. This embodiment ensures that the air pressure is let out of the tire only when there are sufficiently high energy reserves in the vehicle. As a result, it is relatively highly likely that sufficient energy or power for re-inflating the tire is also available after the air pressure has been let out.
Furthermore, it is preferably provided that not only the actual pressure but also a temperature is measured in or on the tire. This temperature, too, is advantageously transmitted wirelessly to the control unit. When actuating the control valve, the control unit can thereby take into account not only the actual pressure but also the temperature.
The invention furthermore encompasses an assembly for tire inflation pressure regulation of a vehicle. The assembly includes a compressed-air source arranged in the non-rotating portion of the vehicle, and also a compressed-air guide from the compressed-air source to the tire of the vehicle. A control valve is arranged in the compressed-air guide. Furthermore, the assembly includes a control unit in the non-rotating portion of the vehicle for actuating the control valve. A sensor is located in the rotating portion of the vehicle, in particular in the wheel bearing, wheel or tire. The sensor serves for determining the actual pressure in the tire. An apparatus for wireless signal transmission is used to transmit the actual pressure to the control unit. The control unit is designed to actuate the control valve, depending on the wirelessly transmitted actual pressure, into a first switch position for inflating the tire and into a second switch position for letting the compressed air out of the tire.
The advantageous embodiments described in the context of the method according to the invention for tire inflation pressure regulation of the vehicle are correspondingly advantageously applicable to the assembly according to the invention for tire inflation pressure regulation of a vehicle.
In particular, it is also provided in the case of the assembly that the control valve can be actuated pneumatically. Accordingly, the control unit is designed to vary the pressure in the compressed-air guide depending on the wirelessly transmitted actual pressure.
The control valve is advantageously located in the rotating portion of the vehicle. The pneumatic actuation of the control valve is suitable particularly in the case of this assembly.
The air pressure in the compressed-air guide is advantageously utilized simultaneously for actuating the control valve and for inflating the tire. There is therefore only one compressed-air guide from the non-rotating portion to the rotating portion and therefore into the tire.
The method according to the invention for tire inflation pressure regulation of the vehicle and the advantageous embodiments described in this respect are correspondingly advantageously applicable to the assembly according to the invention for the compressed air supply of a wheel of a vehicle.
The assembly according to the invention for the compressed air supply of a wheel of a vehicle and the advantageous embodiments described in this respect are correspondingly advantageously applicable to the method according to the invention for tire inflation pressure regulation of the vehicle.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.